As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2010 and are well known to the person skilled in the art.
For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated.
Brazing sheet products find wide applications in heat exchangers and other similar equipment. Conventional brazing sheet products have a core of, typically, but not exclusively an aluminium alloy of the 3xxx-series, having on at least one surface of the core sheet a brazing material or filler material in the form of an aluminium clad brazing layer (also known as an aluminium cladding layer). The aluminium clad layer is made of a 4xxx-series alloy comprising silicon in an amount in the range of 4% to 20% by weight, and preferably in the range of about 6% to 14% by weight. The aluminium clad layer may be coupled or bonded to the core alloy in various ways known in the art, for example by means of roll bonding, cladding spray-forming or semi-continuous or continuous casting processes. These aluminium clad layers have a liquidus temperature typically in the range of about 540° C. to 615° C., and which must be lower than of the core alloy. As used herein, “liquidus temperature” is the temperature at which an aluminium alloy begins to solidify during cooling from its liquid state.
Heat exchangers such as condensers, evaporators and the like for use in car coolers, air conditioning systems, industrial cooling systems, etc. usually comprise a number of heat exchange tubes arranged in parallel between two headers, each tube joined at either end to one of the headers. Corrugated fins are disposed in an airflow clearance between adjacent heat exchange tubes and are brazed to the respective tubes.
There is a demand for brazing sheet material having a good corrosion resistance and high post-braze strength. Ideally such a brazing sheet material is for use in a controlled atmosphere brazing process without the use of brazing fluxes.